Letters from Kevin Walsh in the Arizona State Prison

A Phoenix postmark on a letter mailed from a Tucson Prison???

Some of Kevin's and Laro's letters have been getting odd postmarks.
Since Kevin is jailed in Tucson, Arizona you would expect his letters to
have a Tucson postmark.
And since Laro is jailed in Safford, Arizona you would expect Laro's letters
to have a Safford Postmark or the postmark of the nearest major city to Safford.
But oddly both Laro's and Kevin's letters sometimes have PHOENIX postmarks?

Why?
I don't know!

I asked one dim-bulbed postal clerk, and she said that Safford and Tucson
are subrubs of Phoenix and thus the mail is processed by the Phoenix Postal Center.
Duh!!!!! Lady Tucson is not a surburb of Phoenix!! Tucson is 100 miles south of Phoenix.
Safford is not a surburb of Phoenix either. It is almost on the New Mexico border while Phoenix is in central Arizona!